I am a novice as far as bitcoin is concerned. I lost my priv keys few years back and recently found while going through old lap top. However, I am unsuccessful as When trying to import private key in Bitcoin core v0.23.0 I'm getting:Invalid private key encoding (code -5). Private key starts with 5 and has total 51 digits.

I have created blank wallet in bitcoin-qt and encrypted with passphrase. I request your help. Thanks